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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
* This file is part of the LibreOffice project.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*
* This file incorporates work covered by the following license notice:
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed
* with this work for additional information regarding copyright
* ownership. The ASF licenses this file to you under the Apache
* License, Version 2.0 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of
* the License at http://www.apache.org/licenses/LICENSE-2.0 .
*/
#ifndef SW_BPLUSTREE_HXX
#define SW_BPLUSTREE_HXX
#include <tools/solar.h>
#include <osl/diagnose.h>
#include <swdllapi.h>
#include <stack>
template < class Key, class Value > struct DBPTreeNode;
/** Dense B+ tree implementation (to replace the original BigPtrArray).
This structure is a modification of a B+ tree, see eg. wikipedia:
http://en.wikipedia.org/wiki/B%2B_tree
for the B+ tree implementation.
The problem with 'classic' B+ tree is that it is designed for key/value access
where the key typically is not a sequence of numbers. Consequently, it does
not easily allow inserting in a sense that 'the rest of the values shift to
the right' - but that is the operation that we need to do effectively.
We do a small modification to the B+ tree implementation to make it 'dense' -
the keys are supposed to be a sequence, and if you insert a value, all shifts
to the right. The trick to achieve it is that the values that are stored in
the internal nodes are not absolute, but are relative; so whatever is in the
parents is propagated to the children. That way, shifting half of the tree by
1 to the right after insertion is just a matter of adding 1 to the appropriate
parent.
As part of the removal of BigPtrArray (and consequent refactor of the related
code), this structur is supposed to be a drop-in replacement, with some of
the functionality templatized for easier use.
Key is sal_uLong in the BigPtrArray implementation.
Value is supposed to be SwNodePtr initially.
*/
template < class Key, class Value >
class SW_DLLPUBLIC DenseBPlusTree
{
public:
/// Callback function to be called during ForEach.
typedef bool (*FnForEach)( const Value&, void* pArgs );
public:
DenseBPlusTree();
~DenseBPlusTree();
/// Number of elements.
Key Count() const { return m_nCount; }
/// Insert entry at the specified position.
void Insert( const Value& rValue, Key nPos );
/// Remove nNumber entries starting at the position nPos.
void Remove( Key nPos, Key nNumber = 1 );
/// Insert the value of 'nFrom' to the position 'nTo', and remove the original value.
void Move( Key nFrom, Key nTo );
/// Exchange the value on position pos with the new one.
void Replace( Key nPos, const Value& rValue );
/// Field access.
const Value& operator[]( Key nPos ) const;
/// Traverse over the entire data, and call fn on the data.
void ForEach( FnForEach fn, void* pArgs = NULL );
/// Traverse over the specified range, and call fn on the data.
void ForEach( Key nStart, Key nEnd, FnForEach fn, void* pArgs = NULL );
/// For debugging.
void dump() const;
private:
/// We need to know the exact path from the root to the leaf, including the indexes for various operations
struct NodeWithIndex {
DBPTreeNode< Key, Value > *pNode;
Key nIndex;
NodeWithIndex( DBPTreeNode< Key, Value > *p, Key n ) : pNode( p ), nIndex( n ) {}
};
/// Root of the tree.
DBPTreeNode< Key, Value > *m_pRoot;
/// Amount of values that we contain.
Key m_nCount;
/** Search for the leaf node containing nPos.
@return the leaf node containing nPos
@param pParents stack of parents of the returned tree node so that we can traverse it back to the root
*/
NodeWithIndex findLeaf( Key nPos, std::stack< NodeWithIndex > *pParents = NULL );
/// Shift the right side of the tree to left or right by nHowMuch.
void shiftNodes( const std::stack< NodeWithIndex > &rParents, int nHowMuch );
/// Split the node, and adjust parents accordingly.
DBPTreeNode< Key, Value >* splitNode( DBPTreeNode< Key, Value > *pNode, const std::stack< NodeWithIndex > &rParents, std::stack< NodeWithIndex > &rNewParents );
};
// include the implementation
#include <densebplustree.cxx>
#endif // SW_BPLUSTREE_HXX
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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